Monk, stylite, and author. In spite of a reasonable amount of information, several crucial questions concerning Yuḥanon remain without an answer, due to the fact that so little of his work has survived. It is also unclear whether we are dealing with one person or with more persons having similar names.

First, Yuḥanon is known for his exchange of letters with Yaʿqub of Edessa and with Giwargi bp. of the Arab tribes. Seventeen of the letters by Yaʿqub are addressed to Yuḥanon (Van Ginkel, 78–81), while four extant letters of Giwargi have him as the addressee. One letter written by Yuḥanon himself survives in ms. Brit. Libr. Add. 12,154, f. 291r (see Wright, Catalogue, vol. 2, 988b), but remains unedited. It deals with the prophecy contained in the biblical verse Gen. 49:10, and is addressed to the priest Daniel Ṭuʿoyo (i.e., belonging to the Arab tribe of the Ṭuʿoye); its author is named as ‘Yuḥanon Esṭunoyo in the monastery of Litarba (LYTʾRB)’. Yuḥanon clearly belonged to the network of Syr. intellectuals who discussed in their letters a wide range of topics dealing with history, chronology, philosophy, astronomy, literature, and biblical interpretation. Litarba (LYTʾRB or LYTRYB) is commonly identified with Athareb near Aleppo (see Castellana). Yuḥanon was younger than Yaʿqub and it is generally assumed that he died in 737/8.

Second, Yuḥanon is credited with the authorship of a chronographical work (with a particular interest in chronology), which was used and referred to in the later tradition, esp. in Dionysios of Tel Maḥre and Michael Rabo. Apart from these references and a limited number of quotations, this work, which probably reached to ca. 726/7, is not preserved.

Third, a short grammatical work was preserved in the E.-Syr. ms. Alqosh ( olim ) 139 (or 133?; see J. Vosté, Catalogue de la Bibliothèque syro-chaldéenne du Couvent de Notre-Dame des Semences près d’Alqoš [1929], see 108, ms. 293), which Moberg studied on the basis of a copy provided by A. Scher. Its author is introduced as ‘Yuḥanon Esṭunoyo in the Monastery of Mor Zʿuro near Serugh’. Moberg pointed out this work’s dependence on the grammar of Yaʿqub of Edessa (as well as on the Syr. translation of Dionysius Thrax), but was reluctant to identify the author with Yuḥanon of Litarba.

Fourth, ‘Yuḥanon Esṭunoyo of Beth Mor Zʿuro at Serugh’ (echoing the name of the grammarian) is mentioned as the main character in a theological discussion with an opponent (who poses as a non-Christian and may be a Muslim), of which a brief report is preserved in the Maronite ms. Paris, Bibl. Nat. Syr. 202 (ff. 135v–139r). Whether we are dealing here with the correspondent of Yaʿqub of Edessa (as Suermann assumes) is uncertain (see Hoyland, 516–17).